Apparatus for materials handling



O'ct. 10, 1967 w. B. HULLHoRsT 3,346,128

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APPARATUS FOR MATERIALS-HANDLING Filed May 18, 1965 s sheets-sheet 2- INVENTOR.

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lAPPARATUS FOR'MATERIALS HANDLING Filed May 18, 1965 3 Sheets-Sheet .3

,4 Tram/f V5 United States Patent iiice Patented OC 3 346 128 APPARATUS FR MAIERIALS HANDLING William B. Hullhorst, Granville, Ohio, assignor to Owens- Corning Fiberglas Corporation, a corporation of Delaware Filed May 18, 1965, Ser. No. 456,749 3 Claims. (Cl. 214-6) ABSTRACT THE DISCLOSURE A method and apparatus for stacking mats or sheets of material in proper alignment for later handling or processing which includes means for successively feeding the mats so that they fall into the open top of a bin having at least two opposed walls. Air film bearing surfaces are provided on the interior of each of the opposing walls to engage the edges of the mats to assist the proper fall and alignment thereof into a desired stack.

It has been conventional practice in packaging or preparing fibrous materials, as for example, materials formed of glass fibers, especially useable for insulation purposes, to stack predetermined lengths of fibrous mats in contiguous relation, compress a stack or assembly of mat lengths in a direction normal thereto and insert the compressed assembly into preformed paper bags, sleeves or containers which are sealed or stapled or otherwise closed to enclose the assembly. This method of packaging or conditioning fibrous mats for handling and shipment has been quite expensive for the reasons among others that each mat in each stack must be individually handled to attain a proper size stack for the later compression and insertion into the container. Although previous attempts have been made to stack mats or batts, many diiiiculties have been encountered because of the general lightness of the material and the sail area of the bats if they are being drop stacked. Further diiculties are met in stacking the light fibrous and other types of materials quickly in order to properly supply an automated compressing and packaging station.

It is accordingly an object of this invention to provide an improved method and means for stacking and handling materials.

It is a further object of this invention to provide an improved method and means for handling and stacking materials in which stacking can be accomplished quickly enough to supply stacks to an automated compressing and packaging station.

A still further object of this invention is to provide improved method and means for stacking and handling materials wherein a vast reduction in manual handling is accomplished and wherein superior completed stacks are available.

The invention features apparatus for and a method of material handling which comprises utilizing a bin having an open top to receive objects and conveyor means adapted to move across the open top of the bin. The conveyor has a sucession of platforms to carry objects, the platforms being separated by a succession of openings formed in the conveyor. A stop means is disposed above the conveyor and is operative to arrest movement of an object carried by a platform above the bin so that the platform moves out from under the object and the object falls into the bin through a successive opening in the conveyor. Means are then provided at one side of the bin which are operative to move the collected objects in the bin out of an open side.

More Specifically there is disclosed and featured herein apparatus for handling and stacking mats, batts, boards or the like which comprises a bin having an open top to receive the mats or the like to be stacked. A conveyor means is adapted to move across the open top of the bin and has a plurality of platforms to carry a likev plurality -of mats. The platforms are separated by openings formed in the conveyor. A stop means is disposed above the conveyor and the bin and is operative to arrest movement of a mat carried by the platform. The platform again moves out from under the mat allowing successive mats to fall into the bin and form a stack as successive platforms pass over the bin. A holddown means is advantageously utilized and extends above the mats back along the conveyor from the stop means to prevent the mats from tipping upward as the platform moves out from under the mat. In one embodiment shown herein, means are utilized for pushing a completed stack of mats out of the side of the bin.

In order to attain the greatest speed and efficiency in operation, the total conveyor length of -a platform and a successive opening formed in the conveyor exceeds the individual length of the mats being stacked by an amount sucient only to allow the rear end of a mat carried by a platform to dip into the succeeding opening and below a next successive platform as the mat is arrested by a stop means. In order to provide a compact operation on a frame which may be moved to different feed conveyors, the invention further includes means for guiding the stacking conveyor around the ends and beneath the bin in a closed loop.

The bin advantageously comprises a floor and two end walls. The upper portions of the end walls are preferably liared outwardly to guide the falling mats into stacking relationship between substantially parallel lower portions of the end walls. In one of the embodiments shown herein, a pusher means which is operative to push a completed stack of mats out of the bin for further processing is also constructed to prevent mats from falling out of the bin on the side on which the pusher means is located. Means were also shown for retaining the mats in the bin on the side opposite the pusher means and comprises at least one retaining element extending vertically along the open side and hingedly connected to swing toward and away from the open side. Means for yieldingly biasing the retaining element toward the open side causes the retaining element to prevent the mats from falling out of the open side while allowing the retaining element to be pushed to one side as a completed stack is pushed from the bin for further processing. Another similar retaining element may be disposed at the other end of the open `side and be similarly hinged and biased.

When the mats, batts, etc. are of brous material or are particularly light in density or have large sail areas it is advantageous to provide at least one shelf means disposed intermediate the open top of the bin and the bottom of the bin to receive the falling mats in a partial stack. In response to a predetermined number of mats in a partial stack on the shelf means, there is provided means for withdrawing the shelf from beneath the stack and allowing the partial stack to fall to the bottom of the bin. The mats continue to fall upon a top of the partial stack but their falling distance is much less than it would have been had the withdrawable shelf means not been utilized. Thus a neater stack is attained and, withv the shelf in its original position intermediate the top and bottom of the bin.

A modification of the invention features a bin which comprises two end walls and a fioor means wherein the floor means includes a second conveyor means for moving a completed stack out of the 'bin area 4for further processing.

A plurality of the shelf means may be disposed in spaced relationship between the top and bottom of the bin. Means responsive to predetermined numbers of mats on each shelf means may be utilized for successively withdrawing each shelf means from beneath each partial stack accumulated on an individual shelf means. The withdrawals begin, of course, with the uppermost shelf means and continue downwardly until all shelf means have been withdrawn and a stack is deposited on the bottom of the bin.

The invention thus also features a method of stacking mats of fibrous material or the like which comprises the steps of successively dropping mats into a bin on a shelf intermediate the top and bottom of the bin until part of a stack has built up, removing the shelf means from beneath the partial stack allowing the partial stack to fall to the bottom of the bin, and successively, dropping additional mats on top of the -partial stack until a desired height stack is attained.

Other objects, advantages and features of this invention will become apparent when the following description is taken in conjunction with the accompanying drawings, in Which:

FIGURE 1 is a View in perspective of apparatus embodying the teachings of this invention;

FIGURE 2 is a side elevational view of the apparatus illustrated in FIGURE 1;

FIGURE 3 is a view in perspective of the conveyor means that is utilized in the apparatus of FIGURE 1 illustrating the respective spacings of conveyor platforms and openings formed in the conveyor;

FIGURE 4 is an end elevational view of the apparatus of FIGURE 1;

FIGURE 5 is la view in perspective of apparatus illustrating a second embodiment of the teachings of this invention;

FIGURE 6 is an end elevational view taken in Vertical section of a third embodiment of the teachings of this invention; and

FIGURE 7 is a diagram of a circuit that may be utilized in the operation of the teachings of this invention.

Referring to FIGURES 1 through 4, there is illustrated a first embodiment of the teachings -of this invention. It is to be noted that although this invention is described with reference to the handling and stacking of mats, batts, or boards of fibrous materials, that the teachings are equally applicable for the stacking of any other objects required to be handled in a similar manner.

The stacking apparatus is supported by a frame generally indicated at 50 having vertical end support or leg members 51 and horizontal structural members 52. A -bin 60 is disposed within the frame 50 and comprises, in the embodiment shown, end walls 61 and '62 and a fioor means 63. The upper portions 65 and 64 of walls 61 and 62 are advantageously flared outwardly to receive and guide mats falling from the conveyor means, to be described hereinafter, down between the substantially parallel lower portions of the walls to the floor means 63. A conveyor means generally indicated at 70 (best seen in FIGURE 3) is mounted within frame 50 and comprises a series of platforms supported between conveyor chains 71, 72. The platforms are separated by successive openings 74 formed in the conveyor 70. The conveyor chains 71, 72 are guided on sprocket or other guide wheels 76 mounted on shafts 77. The shafts 77 are journaled in pillow blocks or other bearing means 78 which -are attached to the frame 50. Referring to FIGURE 1, there is illustrated a drive wheel or sprocket gear 79 secured 4 to a shaft 77 of one of the guide sprockets 76. Suitable drive means may be used to drive the conveyor via the drive wheel or sprocket gear 79. Preferably, the drive means synchronizes the stacking conveyor and a feed conveyor which brings mats for stacking.

A stop means 30 is shown located on top of the frame 50 above the bin 60 and the conveyor means 70. A holddown means 81 is shown secured to the stop means 80 and extending back over the bin and conveyor means to prevent the batts from tipping upwardly as a platform moves out from under them. The holddown means may have an upwardly fiared portion 82 to insure that all sizes of mats are properly guided beneath the holddown means 81 without prematurely being arrested in their forward movement. A pusher means in the form of a rack is shown disposed at one side of the bin so that when a stack is completed it may be pushed from bin 60 onto conveyor (FIG. 2). The pusher means 90 may be an open rack as shown with a bracing rack 91 connecting it to a drive shaft 92 (FIG. 3 The drive shaft 92 may be connected to any suitable reciprocating mechanism known in the prior art.

In operation the apparatus of FIGURES 1 to 4 receives or is fed mats consecutively as by a feed conveyor 110 (FIGURE 2) which may have .push knobs 111 formed on the belt thereof to insure that -a mat 112 is pushed all the way off of 4feed conveyor 110 onto the stacking conveyor 70. The feed conveyor and the stacking conveyors should be synchronized so that the leading edge of a mat 112, as it is discharged from conveyor 110, substantially coincides with the leading edge of a platform 73 as such platform rises at the left side of the apparatus. After the mat 112 is transferred to a platform 73, it is conveyed forwardly until a st-op means 80 arrests the forward movement of the mat 112. As the platform 73 moves out from under mat 112, the trailing or rear end of the mat 112 will dip into the opening 74 formed between successive platforms 73. The holddown means 81 is operative then to prevent the mat fr-om tipping upwardly as the platform moves out from under the mat. When the platform moves all the way out from under the mat 112, the mat 112 falls into bin 60. Successively received mats are similarly stacked until `a completed stack is achieved.

A counter may be utilized to count the number of mats `being fed to the stacking apparatus and when a predetermined count is reached, the pusher means 90 may be actuated to push the completed stack from the bin y60 onto the conveyor 115 for further processing.

As an aid in assisting the proper -fall of the mats 112 from the platform 73 of the conveyor, air film bearing surfaces have been provided. At each end wall 61 and 62 a plenum 100 has -been attached and supplied with positive air pressure via flexible conduits 102 attached to an air supply, not shown. Perforations 103 formed in end walls 61 and 62 provide communication between the plenums 100 and the interior surfaces of the walls 61, 62. Thus an air film bearing surface is provided to assist the mats in their falling to maintain the proper stacking relationship. The air film bearing surfaces thus provided may also ibe utilized to assist the pusher means 90 when a completed stack is to be moved onto the conveyor 11-5. That is, a positive air pressure through the perforations 103 will provide air film bearing surfaces between the end walls 61, 62 and the ends of the stack of mats thus reducing the Afriction and therefore the drive required to move the stacks from the bin 60 onto the conveyor 115.

Referring to FIGURE 5, there is illustrated a second embodiment of the teachings of this invention. In one modification the pusher means 90 shown in the preceding embodiment has been replaced by a conveyor means having an upper half 131 of its loop which acts as the bottom of the bin means 60. Thus when mats are stacked as described hereinbefore, instead -of utilizing a pusher means to move the stack onto an adjacent conveyor, the conveyor 130 may simply be indexed one position forward and a portion of the upper half 131 of the conveyor 130 will again be available for the next stack of mats. The conveyor embodiment illustrated in FIGURE is best utilized wherein stacks of mats on the conveyor 130 are fed directly into an automated compressing and packaging station.

Referring to FIGURE 4 there is illustrated an end elevational view of the apparatus of FIGURE 1 best showing side guards 84 and 85 for the mats 112 to prevent their slipping sideways on the platforms 73 as the platforms move out from under them. One of the side guards 84 may be secured permanently in place to a side rail. The other side guard such as 85 may be made adju-stable as with a holddown, knurled head screw means 86 which passes through a slot formed in the guard 85 and is received into a tapped screw aperture formed in a side or horizontal member of the frame. While only the end views of the guards 84 and 85 have been shown, it is to be understood that they are longitudinally extending elements which may be preferably of the cross-section shown.

An additional modification illustrated in FIGURE 5 includes means to prevent mats or batts from accidentally sailing out of the bin or sliding out of properly stacked relationship. There are shown vertical retainer elements 135 which may be hingedly or pivotally connected to the frame 52 at 136 or to the bin wall as at 137. The hinging or pivoting mechanism is preferably spring biased so that the retainer element is urged toward the open side of the bin 60 and defines a closure with the respective end wall with which it is associated. As a complete stack of mats or batts is moved out of the side of the bin, the spring bias is overcome and the retainer elements are pushed back parallel with the bin walls 61, 62 until the pushed or otherwise moved stack of mats is clear of the bin. Then the biasing urges the retainer elements back toward their closed position. When a conveyor such as 130 is utilized as a bottom wall of the bin 60 as in FIGURE 5, it is desirable to utilize retainer elements 140 on both open sides of the bin 60.

Referring to FIGURE 6 there is illustrated a third embodiment of the teachings of this invention for use when the batts or other objects being stacked are of a particular light density or have a large sail area, or are apt to not fall in the proper stacking relationship when the distance of the fall from the top of the bin to the bottom of the bin is too great.

There are illustrated shelf means 141 and 151, which may each comprise a horizontal row of hydraulic rods to form a shelf although only individual units have been shown. Hydraulic means 140 and 150 for operating the shelf means 141 and 151 include piston means 142, 152 secured to rods 141, 151 and slidably journaled in cylinders 143, 153. Reversible pumps 144, 154 are connected to pump a hydraulic fluid to the proper side of the pistons 142, 152 to either withdraw the shelves 141, 151 or place the shelves in the position as shown in FIGURE 6. The shelf means 141, 151 may have depending therefrom iianges or fingers 145, 155 so that the shelf means 141, 151 may be hydraulically actuated to push with fingers or flanges 145, 155 against a completed stack of mats to push the stack from the bin 60 for further processing. If the desired height of the stack places it above the flanges 145, 155 and the density of the material is insufficient to retain the mats in the proper stacked relationship when pushing only at the bottom portion of the stack, an additional Outrigger means 160 may be utilized. Outrigger means 161 is shown as a vertical rod and is representative of a vertical row of rods connected to a horizontal row of rods 141 forming the uppermost shelf means and is to be utilized for pushing. The rod 161 is connected to a piston 162 which is slidable in a cylinder 163 formed within flange or depending finger 145. A reversible pump 164 is connected to pump hydraulic fluid to the proper sides of the cylinder 162 to cause the Outrigger means 161 to raise or lower as desired.

The operation of the apparatus illustrated in FIGURE 6 may be best understood by referring to a circuit diagram illustrated in FIGURE 7. It will be noted in FIGURE 7 that a numbered line diagram has been utilized to illustrate the circuitry. The components can be readily located by reference to the line number where the component is positioned. Further, contact switching operations may be noted without designating a mechanical tie between the contact and the actuating means. The contacts may be located at any convenient position, even though quite remote from their actuating means. Cross reference between the actuating means and its associated contacts is easily accomplished by noting in the right-hand margin of the drawing the reference character of the actuating means, for example LPR, a relay adjacent the line 15 in FIGURE 7, the line at which contact actuating means LPR appears. Following the reference character there are noted the line numbers in which LPR contacts close when caused to do so by the actuating means, i.e., line numbers 33 and 41. Other actuating means and their associated contacts are similarly noted. For example, the actuating coil of the relay PUSH is positioned in line 18. After the reference character designation PUSH in the right-hand margin of the drawing there are noted line numbers 27 and 35. This, as above, denotes PUSH contacts which will be operated in those lines upon actuation of the relay coil PUSH in line 18.

In the operation of the apparatus illustrated in FIGURE 6, a counter 120, shown in lines 10 to 18 of FIGURE 7, may be utilized which provides an output signal as each mat passes. Referring to the counter in FIGURE 7 it will be noted that there are nine terminals from which outputs will be produced as nine mats successively pass the sensing means 121 of the counter 120. The counter may be positioned adjacent the feed conveyor as illustrated in FIG- URE 2. As the first mat passes the counter, an output is produced from terminal 1 and energizes the OPR relay in line 10. Contacts OPR thus close in line 43 and complete a circuit through relay coil H6 and pressure sensitive contacts PS6 to Outrigger pump 164. The energization of relay H6 closes contacts H6 in line 45 enabling a holding circuit around the contacts OPR in line 43. The Outrigger pump 164 is now energized to pump fluid above the cylinder head 162 and close the Outrigger rod 161 to be withdrawn into cylinder 163. The OPR contacts open as the signal is removed from terminal 1 but the circuit is maintained through H6 contacts in line 45. When the rod 161 is fully withdrawn into the cylinder 163, a pressure sensitive switch senses a build up of pressure in cylinder 163 and opens contacts PS6 in line 43. This interrupts the holding circuit through contacts H6 and the circuit is disabled.

When mat number three passes the counter an output is produced from terminal 3 to energize relay UPR in line 12. Contacts UPR close in line 25 to energize relay H1. Contacts H1 close in line 23 to form a holding circuit around contacts UPR in line 25. Upper pump 144 is energized to pump fluid to the stacker side of piston 142 and cause shelf means 141 to be withdrawn from beneath the partially completed stack of mats it has been supporting. Again when the shelf means 141 reaches its fully withdrawn position, pressure switch PS1 senses a pressure buildup and contacts PS1 in line 25 open, breaking the holding circuit for and disabling or deenergizing upper pump 144.

As mat num-ber 6 passes counter 120, an outp-ut is produced from terminal `6 to energize relay LPR in line 15. Contacts LPR close in line 33 energizing holding relay H2. H2 contacts in line 31 close to form -a holding circuit and to maintain the lower pump 154 energized. The lower pump 154 pumps fluid to the stacker side of the piston 152 and causes the withdrawal of shelf means 151. When the shelf means 151 reaches its fully withdrawn position, pressure switch PS2 detects a buildup in pressure and momentarily opens PS2 contacts in line 33 fbreaking the holding circuit to contacts H2 in line 31. At the same time LPR contacts have closed in line 41 energizing holding relay H5. Contacts H5 close in line 39 to form a holding circuit and to energize Outrigger pump 164 in the opposite direction. Fluid is now pumped to the lower side of piston 162 and the Outrigger 161 is raised behind the stack of mats being formed in the bin 60.

As mat number nine passes the counter, a signal is produced at terminal 9 which energizes the PUSH relay in line 18. The contacts PUSH close in line 27 energizing holding relay H3. Contacts H3 close in line 29 to form a holding circuit and to energize upper pump 144 in the opposite direction. At the same time contacts PUSH close in line 35 energizing holding relay H4. Contacts H4 close in line 37 :forming a holding circuit land energizing lower pump 154 in the same direction as upper pump 144. Thus the two pumps 144, 154 are operative to pump fluid to the opposite side of pistons 142, 152 and advance shelf means 141, 151 with the aid of depending anges 145, 155 push the stack from the bin 60 for further processing. It will be noted that Outrigger 161 was also raised so that a full pushing side was available to move a stack out of bin 60.

The shelf means 141, 151 are now in position for another cycle and as the rst mat of the next stack passes the counter 120, a signal is produced at terminal 1 which energizes the OPR relay in line 10 and causes the Outrigger 161 to be lowered as described above. Thus successive stacks of mats may be automatically made and removed from the bin 60. It will be noted that any combination of the generic shelf means described with respect to FIG- URE 6 and/ or the generic pusher means 90 described with respect to FIGURES 1 to 4 may be utilized so that the use of depending anges such as 145, 155 may not be necessary at the end of the shelf means 141, 151.

There has thus been disclosed a method of stacking mats o-f fibrous material or the like which comprises the steps of successively dropping mats or the like into a bin on at least one shelf intermediate the top and bottom of the bin until part of the stack is built up, removing the shelf from beneath said stack allowing the partial stack to fall either to the next shelf below or to` the bottom of the bin, and successively dropping additional mats on top of the partial stacks until the desired height stack is attained.

In conclusion, it is to be noted that the embodiments disclosed and described herein are meant to be illustrative only and not limiting in any sense. The embodiments described serve merely to illustrate the spirit and scope of the invention.

I claim:

1. Apparatus 4for handling and stacking mats or sheets of .material or the like comprising a bin Imeans having an open top, at least two opposed walls and a bottom means; means for successively feeding mats to said bin so that they :fall into the open top thereof; means for providing an air film bearing surface on the interior of each of said opposed walls to engage the edges of and to aid in assisting the proper fall and alignment of said mats in a stack in said bin and to reduce friction between said stack and said walls of said .bin to prevent misalignment of said stack on removal from said bin; means Ifor removing a completed stack of mats from an open side of said bin, said feeding means includes conveyor means adapted to move across the open top of said bin, said conveyor having a plurality of platforms to carry a like plurality of mats, said platforms being separated by openings formed in said conveyor, stop means disposed above said conveyor and said bin and operative to arrest movement of mats carried by said platforms, said platforms moving out from under said mats allowing successive mats to fall into said bin, and hold-down means extending above said mats back along said conveyor from said stop .means to prevent said mats from tipping upward as said platforms move out from under same.

2. Apparatus as defined in claim 1 which further includes at least one shelf means disposed intermediate the open top of said bin and said bottom means to receive said falling mats in a partial stack, and means responsive to a predetermined number of mats in a partial stack for Awithdrawing said shelf from beneath said partial stack allowing it to fall to the bottom of said bin.

3. Apparatus as defined in claim 1 which further includes means for preventing mats from yfalling out the remaining side of said bin and means for retaining said mats in said bin on said one open side, said retaining means comprising at least one retaining element extending vertically along said one open side near one of said opposed walls and pivotally mounted to swing toward and away from said one open side, and means for yieldingly biasing said retaining element toward said one open side so that said retaining element defines a closure with said one opposed wall until the bias is overcome by la stack o-f mats being moved out of said bin.

References Cited UNITED STATES PATENTS 2,000,273 5/1935 `Conklin et al 214-6 2,333,479 11/ 1943 Graf 214-6 2,593,343 4/1952 Rayburn et al 214-6 2,631,759 3/1953 Hoopes 302-29 2,815,870 12/1957 Laub 214-6 2,895,552 7/1959 Romper 214-6 2,901,952 9/1959 Taylor 214-6 3,017,041 1/1962 Hawkes et al 214-6 3,054,515 9/1962 Nawman 214-6 3,270,630 9/1966 Frappier et al 214-6 FOREIGN PATENTS 1,288,044 2/ 1962 France.

142,568 4/1961 U.S.S.R.

GERALD M. FORLENZA, Primary Examiner.

I. E. OLDS, Assistant Examiner. 

1. APPARATUS FOR HANDLING AND STACKING MATS OR SHEETS OF MATERIAL OR THE LIKE COMPRISING A BIN MEANS HAVING AN OPEN TOP, AT LEAST TWO OPPOSED WALLS AND A BOTTOM MEANS; MEANS FOR SUCCESSIVELY FEEDING MATS TO SAID BIN SO THAT THEY FALL INTO THE OPEN TOP THEREOF; MEANS FOR PROVIDING AN AIR FILM BEARING SURFACE ON THE INTERIOR OF EACH OF SAID OPPOSED WALLS TO ENGAGE THE EDGES OF AND TO AID IN ASSISTING THE PROPER FALL AND ALIGNMENT OF SAID MATS IN A STACK IN SAID BIN AND TO REDUCE FRICTION BETWEEN SAID STACK AND SAID WALLS OF SAID BIN TO PREVENT MISALIGNMENT OF SAID STACK ON REMOVAL FROM SAID BIN; MEANS FOR REMOVING A COMPLETED STACK OF MATS FROM AN OPEN SIDE OF SAID BIN, SAID FEEDING MEANS INCLUDES CONVEYOR MEANS ADAPTED TO MOVE ACROSS THE OPEN TOP OF SAID BIN, SAID CONVEYOR HAVING A PLURALITY OF PLATFORMS TO CARRY A LIKE PLURALITY OF MATS, SAID PLATFORMS BEING SEPARATED BY OPENINGS FORMED IN SAID CONVEYOR, STOP MEANS DISPOSED ABOVE SAID CONVEYOR AND SAID BIN AND OPERATIVE TO ARREST MOVEMENT OF MATS CARRIED BY SAID PLATFORMS, SAID PLATFORMS MOVING OUT FROM UNDER SAID MATS ALLOWING SUCCESSIVE MATS TO FALL INTO SAID BIN, AND HOLD-DOWN MEANS EXTENDING ABOVE SAID MATS BACK ALONG SAID CONVEYOR FROM SAID STOP MEANS TO PREVENT SAID MATS FROM TIPPING UPWARD AS SAID PLATFORMS MOVE OUT FROM UNDER SAME. 